In the Third Canto of the Bhagavatam, there is a verse where Brahma was praying to the Lord for the potency to create the universe. Prabhupada explains in the commentary that fortunate is that person who has been entrusted with responsible work, and if he is always conscious that he is subordinate to the will of the Lord, then whatever the result, it will be done nicely. If, however, he is not in that consciousness, even if the result may externally look very nice, the work was still not done properly. Thus, if we are given a particular task, and we put our heart into it, it means that we are always subordinate to Krishna and His representatives. Even though our service may change, the heart should not. The project, whatever it may be, is valueless if we have not put our heart into it. Sometimes Krishna reminds us and puts us into a situation where we have to remember how to keep putting our heart into what He wants us to do.
Lectures From a Disciple Vol 3, Proper Attitude, Pg 229, last paragraph